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Respect X-Forwarded-Proto header #87

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Respect X-Forwarded-Proto header #87

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ad0c43e
Respect X-Forwarded-Proto headers
jellybob Nov 12, 2019
70f79c3
Try moving forwarded proto support after header unwrap
jellybob Nov 12, 2019
83ac77c
Don't touch the headers at all
jellybob Nov 12, 2019
9f1501b
Loosen requirements on async-http to allow git sourcing
jellybob Nov 13, 2019
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2 changes: 1 addition & 1 deletion falcon.gemspec
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,7 @@ Gem::Specification.new do |spec|

spec.add_dependency "async", "~> 1.13"
spec.add_dependency "async-io", "~> 1.22"
spec.add_dependency "async-http", "~> 0.48.0"
spec.add_dependency "async-http"
spec.add_dependency "async-container", "~> 0.14.0"

spec.add_dependency "rack", ">= 1.0"
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3 changes: 2 additions & 1 deletion lib/falcon/adapters/rack.rb
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Expand Up @@ -105,6 +105,7 @@ def unwrap_request(request, env)
# https://tools.ietf.org/html/rfc7239#section-5.4
# https://github.com/rack/rack/issues/1310
env[HTTP_X_FORWARDED_PROTO] ||= request.scheme
env[RACK_URL_SCHEME] = env[HTTP_X_FORWARDED_PROTO]
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Did we set RACK_URL_SCHEME anywhere else or did I just completely miss it?

Also, is this checked by rack linter?

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RACK_URL_SCHEME defaults to request.scheme, however that's not accurate in cases where we're listening on HTTP but have SSL terminated upstream.

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If the user sent the X-Forwarded-Proto: https could that break the application that's running on http? Just wondering if there are security implications to this.

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For context, here's how puma sets RACK_URL_SCHEME:

env[RACK_URL_SCHEME] = default_server_port(env) == PORT_443 ? HTTPS : HTTP

Here's default_server_port:

def default_server_port(env)
  if ['on', HTTPS].include?(env[HTTPS_KEY]) || env[HTTP_X_FORWARDED_PROTO].to_s[0...5] == HTTPS || env[HTTP_X_FORWARDED_SCHEME] == HTTPS || env[HTTP_X_FORWARDED_SSL] == "on"
    PORT_443
  else
    PORT_80
  end
end

In theory if the application was exposed directly, you could bypass middleware to force ssl by sending X-Forwarded-Proto: https. Whether or not that has security implications I don't know, since it could only affect the current user's session.

I'm not certain on this, but I would think it's up to nginx, haproxy, or whatever is used in front of the application to set or reject these headers. Here's how Heroku handles it:

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@sfnelson sfnelson Aug 18, 2023 •
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@ioquatix the purpose of the scheme check is to protect the user from sending information over unencrypted connections. If the user provides the X-Forwarded-Proto: https it will only impact them. I don't think this is a security concern.


if remote_address = request.remote_address
env[REMOTE_ADDR] = remote_address.ip_address if remote_address.ip?
Expand Down Expand Up @@ -157,7 +158,7 @@ def call(request)
}

self.unwrap_request(request, env)

if request.push?
env[RACK_EARLY_HINTS] = EarlyHints.new(request)
end
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22 changes: 22 additions & 0 deletions spec/falcon/adapters/rack_spec.rb
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Expand Up @@ -91,6 +91,28 @@
end
end

context "rack.url_scheme" do
include_context Falcon::Server
let(:protocol) {Async::HTTP::Protocol::HTTP1}

let(:app) do
lambda do |env|
[200, {}, ["Scheme: #{env['rack.url_scheme'].inspect}"]]
end
end

it 'defaults to http' do
response = client.get('/')

expect(response.read).to be == 'Scheme: "http"'
end

it 'responses X-Forwarded-Proto headers' do
response = client.get('/', [["X-Forwarded-Proto", "https"]])

expect(response.read).to be == 'Scheme: "https"'
end
end
context "early hints" do
it_behaves_like Falcon::Adapters::EarlyHints
end
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